CN111226402A - System and apparatus for identifying faults in a radio frequency device or system - Google Patents

System and apparatus for identifying faults in a radio frequency device or system Download PDF

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CN111226402A
CN111226402A CN201880053374.6A CN201880053374A CN111226402A CN 111226402 A CN111226402 A CN 111226402A CN 201880053374 A CN201880053374 A CN 201880053374A CN 111226402 A CN111226402 A CN 111226402A
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test
passive intermodulation
module
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CN111226402B (en
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布伦丹·豪斯菲尔德
穆斯塔法·穆罕默德·塔赫·阿布沙班
弗兰克·约翰·斯特拉坎
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Kaelus Pty Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/10—Monitoring; Testing of transmitters
    • H04B17/15—Performance testing
    • H04B17/17—Detection of non-compliance or faulty performance, e.g. response deviations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G01R23/20—Measurement of non-linear distortion
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/28—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response
    • G01R27/32—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/10—Monitoring; Testing of transmitters
    • H04B17/101—Monitoring; Testing of transmitters for measurement of specific parameters of the transmitter or components thereof
    • H04B17/102—Power radiated at antenna
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/10—Monitoring; Testing of transmitters
    • H04B17/101—Monitoring; Testing of transmitters for measurement of specific parameters of the transmitter or components thereof
    • H04B17/103—Reflected power, e.g. return loss
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/10—Monitoring; Testing of transmitters
    • H04B17/11—Monitoring; Testing of transmitters for calibration
    • H04B17/12—Monitoring; Testing of transmitters for calibration of transmit antennas, e.g. of the amplitude or phase

Abstract

A system for identifying faults in a radio frequency device under test, the system comprising: a passive intermodulation test module configured to perform a passive intermodulation test of the device under test on the at least one test port; and an online S-parameter test set coupled to the passive intermodulation test module and interposed between the passive intermodulation test module and the at least one test port, and configured to perform a wideband S-parameter test of the device under test on the at least one test port.

Description

System and apparatus for identifying faults in a radio frequency device or system
Technical Field
The present invention relates to the identification of faults in Radio Frequency (RF) devices or systems. In particular, although not exclusively, the invention relates to passive intermodulation distortion and scattering parameter testing.
Background
Passive intermodulation distortion (PIM) and scattering parameters (S-parameters) are the most important figures of merit in RF components and communication systems. Both PIM and S parameters are typically measured during the manufacture, installation and commissioning of new RF infrastructures. In particular, PIM and S parameters are used by research and development engineers during the development of new products, by plant personnel during manufacturing processes, and by field personnel when installing or servicing RF components or systems.
Traditionally, measurement of PIM and S parameters requires two different test instruments, a PIM analyser and a Vector Network Analyser (VNA), where each quantity is tested separately. In one prior art approach, PIM and S parameter tests are performed sequentially by separately and manually connecting a PIM analyzer and a VNA to a Device Under Test (DUT).
This approach is inexpensive because it does not require additional hardware or software. However, it has at least two key disadvantages. First, testing is relatively slow to execute because the testing process is interrupted when an operator manually disconnects the PIM analyser and installs the VNA (or vice versa). This is particularly inefficient in high-volume manufacturing environments, where cycle time is an important parameter that must be minimized as much as possible. Secondly, this approach increases the wear on the connector of the DUT, since the connector has to be connected and disconnected from the PIM analyser and again to the VNA.
Attempts have been made to overcome these problems by providing simultaneous connection of the PIM analyser and VNA to the DUT using an RF switch. This method speeds up the testing process because it enables the operator to switch between the two test instruments much faster than manually connecting and disconnecting, and reduces human error. In addition, the use of an RF switch minimizes wear on the DUT's connectors, as it only requires a connection to be made for both tests.
However, the use of RF switches in such tests has a number of disadvantages. In particular, the RF switch must be able to handle RF power levels of perhaps hundreds of watts. Furthermore, the RF switch must have a very low residual PIM, ideally less than-130 dBm with a 2x +43dBm carrier, even after thousands of switching operations. These requirements are practically difficult to meet in RF switches, which results in RF switches that are very expensive, often in the order of thousands of dollars for a single RF switch module.
There is a fault Range (RTF) test module, which is a retrofitable device, that includes an in-line vector reflectometer (in-line reflector) that can be coupled to a PIM analyzer to perform vector PIM and vector reflection coefficient measurements with a single test set and on the same test port. An example of such an RTF module is provided in us patent No. 9,225,441.
Unfortunately, however, and as described in more detail below, the RTF module is limited in that its sweep range in reflectometer mode is limited to the transmit and receive frequency bands of the PIM analyzer to which it is connected. This limitation prevents RTF modules from being used as universal broadband reflectometers, which limits its use to a narrow range of niche applications.
In particular, the vector reflectometer measures the vector reflection coefficient Γ of the DUT by applying a test signal to an input port of the DUT and measuring the amplitude ratio and phase offset between the incident signal "a" and the reflected signal "b" at that portL。
Fig. 1 shows a block diagram of a conventional vector reflectometer test system 100 according to the prior art. Test system 100 includes a vector reflectometer 105 coupled to a DUT110 through a test port 115.
The vector reflectometer 105 includes an RF source 120 for generating a test signal, a forward coupler 125a and a reverse coupler 125b for sampling incident and reflected signals to and from the DUT110, respectively, a pair of coherent receivers 130, 140 for downconverting the sampled signals to a lower Intermediate Frequency (IF), and a detector for measuring the downconverted signal bmAnd amAmplitude/phase detector 135 of the composite ratio.
By performing a suitable calibration procedure before the test starts, the measured results can be post-processed in a computer or microcontroller and the vector reflection coefficient Γ of DUT110 obtainedL。
FIG. 2 shows a block diagram of an online vector reflectometer test system 200 according to the prior art. The test system 200 includes a single port PIM analyzer 205, an online vector reflectometer 210, and a DUT 215.
The in-line reflectometer 210 is a two-port device designed to connect in cascade with another piece of equipment and includes an input port 220 coupled to the single-port PIM analyser 205 and a test port 225 connected to the DUT 215.
Although the input port 220 (also referred to as an "upstream port") connects the reflectometer 210 to the PIM analyser 205, the skilled person will readily appreciate that the online reflectometer 210 may be cascaded with a variety of other devices.
For reflection coefficient measurements, an RF source 230 inside the in-line reflectometer 210 generates a test signal that is coupled by a directional coupler 235 (also referred to as a "source coupler") onto the main RF path in the direction of the DUT 215. The reflectometer then measures the amplitude ratio and phase offset between the incident signal and the reflected signal in the same manner as reflectometer 105 of FIG. 1, and processes these measurements in a computer or microcontroller to calculate the DUT reflection coefficient ΓL。
The online vector reflectometer architecture described above is inherently broadband in design, and in principle can measure over bandwidths of hundreds of megahertz (MHz) or even thousands of MHz (GHz). In practice, however, the operating frequency range of the online reflectometer is limited to the frequency band of the PIM analyser to which it is connected.
In particular, in order to make an accurate reflection coefficient measurement, online reflectometry requires that the output return loss of the PIM analyser be above some minimum threshold, which may be about 6 dB. If this requirement is not met, a pathological situation may arise when measuring a highly reflective DUT, whereby a resonant mode is excited between the PIM analyzer and the DUT at a particular frequency. Under these conditions, the resulting accumulation of power inside the in-line reflectometer can saturate the receiver, resulting in a severe loss of accuracy at these frequencies.
The minimum output return loss requirement is often met by PIM analyzers in their transmit and receive frequency bands, with values in the range of 10-15dB, for example. However, outside of their transmit and receive bands, prior art PIM analyzers typically become highly reflective, with a typical output return loss of 1dB or less. As a result, the operating frequency range of the reflectometer in the prior art RTF module has so far been limited to the transmission frequency band of the PIM analyser to which it is connected.
This phenomenon is illustrated in the examples as follows. FIG. 3 shows a block diagram of an online vector reflectometer test system 300 according to the prior art. The test system 300 includes a single port PIM analyzer 305, an online vector reflectometer 210, and a DUT 215.
The PIM analyser 305 is a 1800MHz PIM analyser, the RF front end of which comprises a diplexer 310, the diplexer 310 comprising a transmit filter 315a and a receive filter 315b connected together at port 220 by means of a pair of carefully selected transmission lines 320, the transmission lines 320 often being referred to as a "manifold".
The use of a manifold-coupled duplexer 310 along with associated variants (e.g., respective triplexers and quadplexers) for combining transmit and receive bands onto the shared port 220 in this manner is used in all commercially available PIM analyzers.
One of the characteristics of these manifold-coupled duplexers, triplexers and quadplexers is that they are highly reflective at frequencies outside their pass-bands. Consider the aforementioned output return loss response 400 of the 1800MHz duplexer 310 shown in figure 4.
In the receive and transmit bands 405a, 405b of the duplexer 310 spanning the frequency ranges of 1710-. Outside these bands 405a, 405b, however, the output return loss is close to 0 dB.
The highly reflective behavior of the duplexer 310 in its stop band can cause problems for the in-line reflectometer 210 if the DUT 215 is also highly reflective. In particular, at certain critical frequencies related to the electrical distance between the duplexer 310 and the DUT 215, the phase of the duplexer's output reflection coefficient, and the phase of the DUT's input reflection coefficient, a resonant mode may be excited that causes a large amount of power to accumulate between the duplexer 310 and the DUT 215. This in turn increases the amount of power entering the reflectometer 210 via the forward coupler 125a and the reverse coupler 125b of the reflectometer 210. In extreme cases, the power rise caused by this resonance may be sufficient to saturate the reflectometer receiver, causing a severe loss of measurement accuracy at these frequencies.
This phenomenon is illustrated in fig. 5, which shows an analog output 500 during measurement scanning of a highly reflective DUT 215 (e.g., and in this case, an open-circuit length of a transmission line), including analog outputs 505a, 505b from the forward coupler 125a and the reverse coupler 125b, respectively, in the reflectometer 210 of fig. 3.
As shown in fig. 5, in the transmit band 405a and receive band 405b of the PIM analyser 305, where the instrument output return loss is high, the outputs 505a, 505b from the reflectometer forward coupler 125a and reverse coupler 125b, respectively, are relatively constant, exhibiting only a few dB of variation within these bands.
In contrast, at frequencies outside the transmit band 405a and the receive band 405b of the PIM analyser 305 where the instrument's output return loss is very low, the outputs 505a, 505b from the reflectometer's forward coupler 125a and reverse coupler 125b, respectively, exhibit large amplitude variations with frequency, rising up to 30dB above the levels observed in the transmit band 405a and receive band 405 b. In most real online reflectometers (including existing RF modules), this rise is sufficient to saturate both receivers, causing a severe loss of measurement accuracy at these frequencies.
Further insight into the conditions necessary for a resonant mode to be excited between the PIM analyser 305 and the DUT 215 can be obtained from an approximate mathematical model of the signal entering the reflectometer 210 during the measurement scan.
The mathematical model is based on the reflectometer 210 of fig. 2 and 3 with termination impedances attached to the port 220 and the test port 225. The termination impedance represents the reflection coefficient Γ of the PIM analyzers 205, 305 and DUT 215, respectivelySAnd ΓL。
The following analysis assumes that the insertion loss between the upstream port 220 and the test port 225 of the reflectometer is negligible and that the source coupler 235, the forward coupler 125a and the reverse coupler 125b are all loosely coupled to the main RF path through the reflectometer.
During a survey scan, an RF source 230 inside the reflectometer 210 generates a test signal a1The test signal is coupled onto the main RF path in the direction of the DUT 215 via the source coupler 235. The forward going test signal is sampled by the forward coupler 125a and the signal reflected from the DUT 215 is sampled by the reverse coupler 125 b.
Let amRepresenting the output signal from the forward coupler, and bmRepresents the output signal from the inverse coupler:
Figure BDA0002385475090000051
Figure BDA0002385475090000052
wherein
a1Test signal from reflectometer internal RF source
amSignal at the output of a forward coupler
bmSignal at the output of the inverse coupler
Cs、CfAnd CrGround source coupler, forward direction, respectivelyCoupling coefficient of coupler and inverse coupler
DfAnd DrDirectivity of forward and reverse couplers, respectively
ΓSAnd ΓLComplex reflection coefficient of PIM analyzer and DUT respectively
θ — electrical length of transmission line between PIM analyzer and DUT, including electrical length of reflectometer
Equation 1 and equation 2 share a common denominator (1- Γ)LΓSe-j2θ) It is at a minimum whenever the following phase condition is satisfied:
∠ΓS+∠ΓL-2 θ ═ 2n pi (n ═ 0,1,2, …) (equation 3)
Wherein
∠ΓSPhase of output reflection coefficient of PIM analyzer
∠ΓLPhase of input reflection coefficient of DUT
The magnitude of the output reflection coefficient of the PIM analyzer, | Γ, when the reflectometer is performing an in-band measurementSI is close to zero. This means the denominator (1- Γ)LΓSe-j2θ) The minimum possible value of (c) is always close to 1 regardless of whether the phase condition in equation 3 is satisfied. Under these conditions, amAnd bmIs guaranteed to be for a range | ΓLGamma within 1 |LAll values of (a) are finite.
Conversely, when the reflectometer makes an out-of-band return loss measurement, the magnitude of the output reflection coefficient of the PIM analyzer, | ΓSL is usually close to 1. If the DUT is highly reflective at the frequency of interest, the magnitude of the input reflection coefficient of the DUT | ΓLWill also approach 1. Under these conditions, if the phase condition in equation 3 is satisfied at the same time, the denominator (1- Γ)LΓSe-j2θ) Will approach zero, and amAnd bmWill be close to infinity and is clearly a very undesirable result.
Accordingly, there is a clear need for improved systems and apparatus for identifying faults in radio frequency devices or systems.
It will be clearly understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms part of the common general knowledge in the art in australia or in any other country.
Summary of The Invention
The present invention is directed to a system and apparatus for identifying faults in radio frequency devices or systems that may at least partially overcome at least one of the above disadvantages or provide the consumer with a useful or commercial choice.
In view of the foregoing, the present invention resides broadly in one form in a system for identifying faults in a radio frequency Device Under Test (DUT), the system comprising:
a Passive Intermodulation (PIM) test module configured to perform a passive intermodulation test of a device under test on at least one test port; and
an online S-parameter test set coupled to the passive intermodulation test module and interposed between the passive intermodulation test module and the at least one test port, and configured to perform a wideband S-parameter test of the device under test on the at least one test port.
In yet another form, the invention resides broadly in a system for identifying faults in a radio frequency device under test, the system comprising a passive intermodulation test module configured to perform a passive intermodulation test of the device under test on at least one test port,
the passive intermodulation test module comprises:
a transmit module configured to provide at least one test signal on at least one test port for passive intermodulation testing of a device under test; and
a receiving module configured to receive, on the at least one test port, a passive intermodulation signal generated by the device under test in response to the test signal.
The transmit module and the receive module may be coupled to the at least one test port by a reflection-free multiplexer. The reflectionless multiplexer may be a hybrid-coupled multiplexer.
Advantageously, the system enables passive intermodulation and wideband S-parameter testing without requiring any physical connection changes on at least one test port between the passive intermodulation test and the wideband S-parameter test, and without requiring RF switching between the passive intermodulation test module and the online S-parameter test set. The system can advantageously achieve accurate broadband S-parameter testing even if the DUT is highly reflective.
Preferably, the in-line S-parameter test set is configured to perform wideband S-parameter tests both inside and outside the transmit and receive bands of the passive intermodulation test module.
The online S parameter test set may include a fault Range (RTF) module.
The online S-parameter test set may include a vector reflectometer.
The at least one test port may comprise a single test port.
The at least one test port may include two test ports. This configuration may enable forward and reverse passive intermodulation testing and/or full dual port S parametric testing in either direction.
The online S-parameter test set may include a two-port online S-parameter test set coupled to first and second ones of the two test ports.
The in-line S-parameter test set may include first and second separate in-line reflectometers, one coupled to each of the first and second test ports of the two test ports.
The online S-parameter test set may include an RF source for generating test signals coupled to one or more test ports through one or more directional couplers. This configuration enables the S-parameter test set to operate as a stand-alone in-line device located between the passive intermodulation analyzer and the DUT.
The passive intermodulation test module may be coupled to an online S-parameter test set by a mixer coupling multiplexer. The hybrid coupling multiplexer may be configured to provide high output return loss over a wide bandwidth.
The mixer-coupled multiplexer may include two or more independent channelized networks connected in cascade, followed by matched loads.
Each channelizing network may include two identical quadrature mixers and a pair of identical filters. Further, each channelized network may correspond to a particular frequency range.
The two or more independent channelization networks may include one channelization network that spans a transmit frequency band of the PIM test module and another channelization network that spans a receive frequency band of the PIM test module.
In one embodiment, the hybrid coupling multiplexer includes a diplexer that includes two independent channelization networks.
The PIM test module may include a multi-band PIM analyzer capable of measuring PIM in two or more non-overlapping cellular frequency bands on a single test port. Optionally, the PIM test module may include a PIM analyser, wherein each emitted carrier is filtered separately before being combined with another carrier at the test port. Again optionally, the PIM test module may include a PIM analyzer having a single transmit frequency band and multiple receive frequency bands.
In an alternative embodiment, the PIM test module may be coupled to the online S-parameter test set by cascading directional filters.
The online S-parameter test set may be configured to provide dynamic source power control.
The online S-parameter test set may be configured to dynamically adjust the stimulation level during the S-parameter measurement scan using a variable attenuator.
The system may include a control system configured to monitor receiver output levels in the online S-parameter test set and adjust the variable attenuator based on the monitored output levels.
The control system may be configured to compare the monitored receiver output level to one or more thresholds and adjust the variable attenuator to adjust the receiver output level to within the one or more thresholds.
The control system may suspend the S parameter measurement scan, adjust the variable attenuator, and restart the S parameter measurement scan using the new attenuator setting. This process may be repeated until the monitored receiver output level is within one or more thresholds at all frequencies of the S-parameter measurement sweep.
A variable attenuator may be provided at the output of the RF source of the S-parameter test set.
The system may include an attenuator between the PIM test module and the online S-parameter test set. The attenuator may improve the output return loss of the PIM analyser. The attenuator may comprise a fixed attenuator.
The PIM test module may be configured to compensate for insertion loss of the attenuator.
The PIM test module may be configured to compensate for insertion loss of the attenuator by amplifying an output signal of the PIM test module. Optionally, the PIM test module may be configured to compensate for the insertion loss of the attenuator by using a pulsed mode of operation, thereby allowing higher power levels to be generated within short time intervals (e.g., 100 milliseconds). Optionally, again, the PIM test module may be configured to compensate for insertion loss of the attenuator by combining two transmit tones (transmit tones) using a duplexer to increase the power output of the PIM test module.
The PIM test module may comprise a multi-port PIM test module, and an attenuator may be mounted to each port of the PIM analyser.
The system may include a pair of in-line vector reflectometers between the attenuator and the DUT.
In another form, the invention resides broadly in a passive intermodulation test module configured to perform a passive intermodulation test of a device under test on at least one port, the passive intermodulation test module comprising:
a transmit module configured to provide at least one test signal on at least one test port for passive intermodulation testing of a DUT; and
a receive module configured to receive, on at least one test port, a passive intermodulation signal generated by the DUT in response to a test signal;
wherein the transmit module and the receive module are coupled to the at least one test port through a reflection-free multiplexer.
The reflectionless multiplexer may be a hybrid-coupled multiplexer. The hybrid coupling multiplexer may be configured to provide high output return loss over a wide bandwidth.
In yet another form, the present invention resides broadly in an online S-parameter test set for use in a system for identifying or locating faults, the online S-parameter test set including:
an RF source for generating a test signal, the RF source coupled between an input and an output of the online S-parameter test set through one or more directional couplers; and
a variable attenuator configured to provide dynamic source power control of the RF source.
The online S-parameter test set may be configured to dynamically adjust stimulation levels during an S-parameter measurement scan.
In yet another form, the present invention resides broadly in a system for identifying faults in a radio frequency Device Under Test (DUT), the system comprising:
at least one input for coupling to a radio frequency device;
at least one output terminal for coupling to a DUT;
an online S-parameter test set coupled between the at least one input and the at least one output and configured to perform broadband S-parameter testing of the DUT; and
an attenuator between the PIM test module and the at least one input.
The attenuator may improve the output return loss of the radio frequency device.
The attenuator may comprise a fixed attenuator.
Any feature described herein may be combined with any one or more of the other features described herein in any combination within the scope of the invention.
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that prior art forms part of the common general knowledge.
Brief Description of Drawings
Various embodiments of the present invention will be described with reference to the accompanying drawings, in which:
FIG. 1 shows a block diagram of a conventional single port vector reflectometer test system according to the prior art;
FIG. 2 shows a block diagram of an online vector reflectometer test system according to the prior art;
FIG. 3 shows a block diagram of an online vector reflectometer test system according to the prior art;
FIG. 4 shows the output return loss response of a 1800MHz duplexer of a test system;
FIG. 5 shows simulated outputs from forward and reverse couplers in a reflectometer of a test system;
FIG. 6 illustrates a system for identifying and/or locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 7 illustrates a block diagram of a known hybrid-coupled multiplexer as configured in accordance with an embodiment of the present invention;
FIG. 8 illustrates a system for identifying and/or locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 9 illustrates a system for identifying and/or locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 10 shows a block diagram of a system for locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 11 shows a block diagram of a system for locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 12 illustrates a method of return loss measurement according to an embodiment of the invention;
FIG. 13 illustrates a system for locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 14 shows a block diagram of a system for locating a fault in a DUT in accordance with an embodiment of the invention;
FIG. 15 shows a block diagram of a system for locating a fault in a DUT in accordance with an embodiment of the invention; and
FIG. 16 shows a block diagram of a system for locating a fault in a DUT according to an embodiment of the invention.
Preferred features, embodiments and variants of the invention will appear from the following detailed description, which provides sufficient information for a person skilled in the art to carry out the invention. The detailed description is not to be taken as limiting the scope of the foregoing summary of the invention in any way.
Description of the embodiments
The following describes systems and methods for identifying and/or locating faults in a DUT in which the above-mentioned frequency limitations are eliminated or reduced.
Briefly, the embodiments of the invention described below address the above-described degradation in reflectance measurement accuracy at the RTF module when testing highly reflective devices at frequencies outside the transmit and receive frequency bands of the PIM analyzer. This enables the RTF module to function as a universal broadband single-port VNA.
The system is described with reference to an online vector reflectometer, an example of which is an RTF module. For clarity, such reflectometers are broadly referred to as "online vector reflectometers" or "online S parameter test sets," but skilled artisans will readily recognize that RTF is an example of such reflectometers.
Fig. 6 illustrates a system for identifying and/or locating a fault in a DUT 605 in accordance with an embodiment of the invention. System 600 uses a common test port to implement switchless PIM and broadband S parametric tests and provide high output return loss over a wide frequency range.
The system 600 includes a PIM analyzer 610 and an online vector reflectometer 615 for PIM and broadband S-parameter tests, respectively. Similar to the system 300 of FIG. 3, the PIM analyzer 610 is coupled to the online vector reflectometer 615 through an input port 620, and the online vector reflectometer 615 is coupled to the DUT 605 through a test port 625.
The PIM analyser 610 is generally of the type disclosed in US patent application publication No. US20090125253 and US patent application publication No. US20090096466, the disclosures of both of which are modified as outlined below, being incorporated herein by reference.
In particular, the PIM analyser 610 comprises a diplexer 630 in the form of a reflection-free multiplexer. Reflectionless multiplexers are capable of providing high output return loss over a wide bandwidth.
In the embodiment of the invention shown in fig. 6, the reflectionless multiplexer is in the form of a hybrid-coupled multiplexer consisting of two independently channelized networks 635a, 635b connected in cascade.
When compared to the PIM analyser 305 of fig. 3, it can be seen that the diplexer 630 changes from a conventional manifold-coupled design (as is the case on the PIM analyser 305) to a hybrid-coupled multiplexer design capable of providing high output return loss over a wide bandwidth.
Fig. 7 illustrates a block diagram of a known hybrid coupling multiplexer 700 configured in accordance with an embodiment of the present invention. The mixer-coupled multiplexer 700 includes two or more independently channelized networks 705a, 705b, 705n connected in cascade, followed by a matched load 710.
The hybrid coupler diplexer 630 of the PIM analyser 610 is a specific example of a hybrid coupler multiplexer 700 having two channelisation networks 705 (i.e. channelisation networks 635a, 635 b).
Each channelizing network 705 includes two quadrature mixers 715 and a pair of identical filters 720a, 720b, 720 n. In each case, the quadrature hybrid 715 located on the side adjacent to the common port of the multiplexer must be able to operate over a bandwidth equal to the operating frequency range of the in-line vector reflectometer. The quadrature hybrids 716a, 716b, 716n, located on the other side of the filter pairs 720a, 720b, 720n, respectively, need only operate at a bandwidth equal to the bandwidth of the filter pair to which they are connected. Thus, these quadrature hybrids 716a, 716b, 716n may be designed to have less stringent specifications than quadrature hybrids 715 located on the side adjacent to the common port. Each channelized network 705 corresponds to a particular frequency f1, f2, fn, and each pair of filters 720a, 720b, 720n is designed to pass the frequency corresponding to that channel 705, while rejecting any other frequencies.
Thus, a signal entering the multiplexer 700 will propagate through the cascade of channelized networks 705a, 705b, 705n until it encounters the channel 705, the passband of the channel 705 spanning the frequency range occupied by the signal. The signal enters that channel 705 and is absorbed by the following circuitry.
If the signal does not fall within the pass band of any channel 705 in the multiplexer 700, the signal continues through the network until it is absorbed by the matched load 710 located after the last channel 705 in the cascade.
Theoretically, the hybrid coupling multiplexer 700 has infinite output return loss over the entire infinite frequency range with an ideal quadrature hybrid, identically tuned filter pair, perfectly matched termination at the output of each channel, and perfectly matched termination 710 after the last channel 705 in the cascade. In practice, however, it is possible to use a limited bandwidth quadrature hybrid and an incompletely tuned filter pair, while providing an output return loss that far exceeds the output return loss that can be achieved with a manifold-coupled multiplexer (e.g., duplexer 310), both in terms of return loss magnitude and bandwidth.
Returning again to fig. 6, when incorporated into the system 600, the mixer-coupled multiplexer requires only two channels, one across the transmit band of the PIM analyser 610 and the other across the receive band.
The PIM analyser 610 presents a well-matched broadband load at port 620 which eliminates the risk of exciting resonant modes when the online reflectometer 615 performs reflection coefficient measurements while the DUT 605 is reflective. Thus, unlike the system 300 of fig. 3, the PIM analyzer 610 enables the online reflectometer 615 to obtain high measurement accuracy at a wide range of frequencies, including frequencies outside of the transmit and receive frequency bands of the PIM analyzer 610.
Another advantage of the mixer-coupled multiplexer architecture described in fig. 7 and incorporated into system 600 is that it allows any number of non-overlapping channels 705 to be added in cascade. This enables a variety of alternative PIM analyser configurations, including: a) a multi-band PIM analyzer capable of measuring PIM in two or more non-overlapping cellular frequency bands on a single test port; b) rather than combining the carriers at the transmitter output and then passing both carriers through a common filter, a PIM analyser, in which each transmitted carrier is filtered separately before being combined with another carrier at the test port, is much more efficient than: combining the two carrier powers with a Wilkinson combiner or quadrature hybrid whereby half of the RF power is lost in the combining process; and c) a PIM analyzer having a single transmit frequency band and multiple receive frequency bands.
However, skilled artisans will readily recognize that a hybrid-coupled multiplexer is just one example of a reflectionless multiplexer. The reflectionless multiplexer may be configured to achieve a desired improvement in output return loss for the PIM analyzer.
In the context of the present invention, it is to be understood that the term "non-reflective" is not intended to be literally understood. In practice, all radio communication devices tend to reflect some portion of the signal power applied to their input and output ports. Furthermore, such devices typically have a limited operating bandwidth beyond which their return loss performance degrades rapidly. In the context of the present invention, the term "reflection-free" stands for a multiplexer whose output return loss is sufficiently high over a sufficiently wide frequency range to ensure that the measured signal level inside the test set remains below the compression point of the receiver of the test set at all frequencies within the operating frequency range of the test set when the multiplexer is connected to the upstream port of the online S-parameter test set.
A multiplexer with an output return loss of 3dB over a 20MHz frequency range can be considered a reflectionless multiplexer, depending on the particular architecture of the on-line S-parameter test set to which the multiplexer is connected. In another exemplary embodiment, the reflectionless multiplexer may be configured to provide an output return loss of 10dB over a 1000MHz bandwidth, so as to achieve a sufficiently high output return loss over a sufficiently wide frequency range to ensure that the measured signal level inside the test set remains below the compression point of the receiver of the test set at all frequencies within the operating frequency range of the test set when the multiplexer is connected to the upstream port of the online S-parameter test set.
In addition to the high output return loss property, the reflectionless multiplexer may possess many of the same properties as a conventional manifold-coupled multiplexer in order to be suitable for use in a PIM analyzer. The list of required attributes may include: very low residual passive intermodulation levels (typically better than-125 dBm with a 2x43dBm carrier); high transmit-to-receive isolation (typically 80-100 dB); high power processing capability in the transmit band of the PIM analyser; low insertion loss in the transmit and receive bands of the PIM analyzer; and wide stop bands in the transmit and receive paths of the multiplexer to prevent out-of-band noise, external interference, transmitter harmonics, and image band signals from entering the receiver of the PIM analyser and degrading its measurement accuracy.
The reflectionless multiplexer may be embodied in various configurations and architectures. Examples of reflectionless multiplexer architectures include cascaded directional filters, manifold-coupled multiplexers with redundant channels, and circulator-coupled multiplexers in addition to the hybrid-coupled multiplexers mentioned above. Each of these provides advantages and disadvantages.
The cascaded directional filter based reflectionless multiplexer is functionally similar to a mixer-coupled multiplexer. Potential advantages of this configuration over the mixer coupling configuration include the need for only one filter per channel, whereas the mixer coupling configuration requires two filters per channel. Another advantage is that the directional filter based multiplexer does not require a wideband quadrature mixer and therefore it is possible to provide high output return loss over a much wider frequency range than the mixer coupling configuration. Potential drawbacks of directional filter based multiplexers include difficulties in achieving filter bandwidths greater than 1% and the inability to implement transmission zeros in order to improve filter selectivity.
The manifold coupling multiplexer with redundant channels is the same as a conventional manifold coupling multiplexer, but one or more additional channel filters are added. A low PIM load is mounted to the channel port of the additional filter. The pass bands in the additional filters are selected to span frequency bands between, above and below the transmit and receive filter pass bands. Thus, any signal entering the common port of the multiplexer that falls outside the transmit and receive bands of the PIM analyser, but within the pass band of the additional channel filters, will pass through these filters before being absorbed by the low PIM load on the channel ports of these filters. Thus, the multiplexer achieves high output return loss over the combined frequency range spanned by all filters. The main advantage of the manifold-coupled multiplexer with redundant channels is that the channel filters can be designed with an optimal frequency response based on e.g. the generalized chebyshev function. Disadvantages of manifold coupling multiplexers with redundant channels may include design complexity and tuning difficulties.
The circulator-coupled multiplexer includes a cascaded set of circulators, the last circulator in the cascade terminating at a low PIM load. The third port of each circulator is connected to a channel filter. When used in a PIM analyser, the circulator connected to the transmit channel filter must circulate the signal in the opposite direction to the circulator used by the receive filter. The low PIM load at the end of the circulator cascade gives the network the desired broadband high output return loss response. Potential advantages of circulator coupling multiplexers are simplicity of tuning and modularity of construction. The main drawback is that the circulator generates a relatively large level of passive intermodulation, which is highly undesirable for the multiplexer used in the PIM analyser. However, there may be some applications where this does not pose a problem, for example when performing low power intermodulation measurements on active electronic devices, where the transmit carrier level is in the order of milliwatts or microwatts, rather than 20 watts, as is typically the case when testing according to the IEC-62037 standard. In this case the passive intermodulation generated by the circulator will be negligible compared to the active intermodulation generated by the electronic circuit under test. Another potential drawback of circulator-coupled multiplexers is the fact that many commercially available circulators are not very wide in bandwidth, limiting the frequency range over which high output return loss can be achieved.
Thus, various reflectionless multiplexer architectures (e.g., hybrid coupled multiplexers, cascaded directional filters, manifold coupled multiplexers with redundant channels, or circulator coupled multiplexers) can be used to achieve output return loss that is high enough over a wide enough frequency range to ensure that the measured signal level within the test set remains below the compression point of the receiver of the test set at all frequencies within the test set' S operating frequency range when the multiplexer is connected to the upstream port of the in-line S-parameter test set.
In some embodiments, the system 600 may be extended to provide a dual-port configuration that allows forward and reverse PIM responses, as well as full dual-port S parameters of the DUT, to be measured in either direction. Thus, embodiments of the present invention include a dual port PIM analyzer that is also capable of performing full dual port S parameter measurements without requiring any external connection changes.
Fig. 8 illustrates a system 800 for identifying and/or locating a fault in a DUT 805 according to an embodiment of the invention. System 800 supports dual port switchless PIM and broadband S parameter testing and provides high output return loss over a wide frequency range.
The system 800 includes a dual port PIM analyzer 810 and a dual port online S-parameter test set 815 that implement PIM and broadband S-parameter testing. In particular, PIM analyzer 810 is coupled to online S parameter test set 815 via first input port 820a and second input port 820b, and online S parameter test set 815 is coupled to DUT 805 via first test port 825a and second test port 825 b.
The transmit carrier from the PIM analyzer 810 may be routed to the first input port 820a or the second input port 820b via the first RF switch 835a (and thus through the first mixer coupling duplexer 830a or the second mixer coupling duplexer 830b), and the PIM response of the DUT 805 may be measured by the second RF switch 835b on the first input port 820a or the second input port 820b (and thus through the first mixer coupling duplexer 830a or the second mixer coupling duplexer 830 b). This allows the forward and reverse PIM response of the DUT 805 to be measured in either direction.
One novel aspect of this arrangement is that by virtue of the hybrid-coupled duplexers 830a, 830b in the front-end of the PIM analyzer 810, the system 800 has high output return loss over a wide frequency range on both test ports 825a, 825 b. This facilitates broadband operation of the online S-parameter test set 815 located between the PIM analyzer 810 and the DUT 805.
Skilled artisans will readily recognize that online S parameter test set 815 may be implemented in a variety of ways, some of which will be described below.
Fig. 9 illustrates a system 900 for identifying and/or locating a fault in a DUT 805 according to an embodiment of the invention. The system 900 may be similar or identical to the system 800 of fig. 8 and includes an online S parameter test set 815' interposed between the PIM analyzer 810 and the DUT 805.
System 900 allows all four S parameters (i.e., S) of DUT 80511、S12、S21And S22) The amount of the vector (i.e., the amount that includes both magnitude and phase information) that is measured as a complete error correction is used from which the systematic errors associated with the test set are eliminated.
The online S-parameter test set 815' is similar to a conventional Vector Network Analyzer (VNA) and includes an onboard RF source 905 for generating a test signal, a signal separation network in the form of a forward coupler 910a and a reverse coupler 910b before each test port 825a, 825b, a plurality of coherently tuned receivers 930, 955 for downconverting the forward and reverse coupled signals to an intermediate frequency, and an amplitude and phase detector module 935 for measuring the amplitude ratio and phase offset of the downconverted forward and reverse coupled signals. Test signals from the RF source 905 can be routed to either of the instrument's test ports 825a, 825b by way of the RF switch 945 a. A second RF switch 945b is provided so that the instrument can measure the signal emerging from any of the forward couplers 910a, although in most cases the second switch 945b will be set to the same test port as the switch 945a of the RF source. A third switch 950 is provided so that the instrument can measure the signal emerging from any of the reverse couplers 910 b.
One important difference between the online S-parameter test set 815' and the conventional VNA is that the RF source 905 generating the test signal is not directly connected to the main RF path, but is inserted onto the main RF path via a directional coupler 940 (also referred to as "source coupler"). This enables the S-parameter test set to operate as a stand-alone online device located between the PIM analyser 810 and the DUT 805.
Care must be taken in the design of the S-parameter test set to ensure that it does not compromise the performance of PIM analyzer 810. In particular, the S-parameter test set 815' should have very low residual PIM levels, ideally less than-125 dBm with a 2x +43dBm carrier. In addition, the S-parameter test set must allow the high power transmit carrier from the PIM analyzer 810 to pass through it without suffering damage through dielectric breakdown or overheating.
It is also desirable (but not necessary) for the S-parameter test set to have very low insertion loss in order to minimize its effect on the amplitude of the transmitted carrier. This can be relaxed if the PIM analyser 810 is able to increase its transmit power to compensate for the insertion loss of the S-parameter test set. Finally, to minimize the effect of source and load mismatch on the measurement uncertainty of the PIM analyzer 810, the S-parameter test set should ideally have high input and output return losses.
Prior to testing, the S-parameter test set is first calibrated to correct for systematic errors in the system 900. For this purpose, many methods are available, one of the most well known and accurate being a "full dual port" calibration procedure, also known as a "12-item error correction" procedure or a "10-item error correction" procedure, depending on whether the instrument's inter-port leakage is accounted for in calibration. Details of such methods can be found in Rytling, Keysight Technologies, Hieble, and Anritsu Company.
In an alternative embodiment of the invention, a pair of online vector reflectometers are connected to a test port of a dual port PIM analyzer. FIG. 10 shows a block diagram of a system 1000 for locating a fault in a DUT 805 according to an embodiment of the invention.
The system 1000 includes a two-port PIM analyzer 810 with an online vector reflectometer 1005 on each port. This configuration results in an approximate vector S for the DUT 80511And S22And S12And S21Scalar quantity ofThe amplitude can be measured.
The reflectometer 1005 does not have to share a common frequency reference, but it is necessary that the reflectometer have low PIM and sufficient power handling capability to pass the two carriers from the PIM analyser 810 without suffering damage.
Vector S is made by performing only conventional reflectance measurements with reflectometer 1 or 2, respectively11Or S22And (6) measuring. Due to the fact that it is not possible to correct the load mismatch presented by the PIM analyser 810 on the output port of the DUT 805, the results obtained in this case are typically not as accurate as the results from the S-parameter test set using 10 or 12 error corrections. Despite this limitation, there are many situations in which the system 100 is capable of highly accurate S11And S22And (6) measuring. These cases include when the DUT 805 has a sufficiently high insertion loss to mask the load mismatch presented by the PIM analyser 810 on the output port of the DUT 805 or when the DUT 805 has a low return loss compared to the insertion loss of the DUT 805 and the load mismatch presented by the PIM analyser 810.
The above situation can be summarized as follows, which is equally valid for reciprocal and non-reciprocal devices:
Figure BDA0002385475090000201
wherein
RLDUTInput return loss in dB for a DUT
Figure BDA0002385475090000202
Forward insertion loss in dB for DUT
Figure BDA0002385475090000203
Reverse insertion loss in dB for DUT
RLPIMOutput return loss in dB for PIM analyzer
The values of the parameters in equation 4 should always be written asA positive number. For example, input return loss RL for passive DUTsDUTShould be written as "15 dB" instead of "-15 dB", i.e. a negative sign is implicit in the word "loss".
If the DUT is a reciprocal device, equation 4 can be simplified as:
RLDUT≤(2×ILDUT)+RLPIM-20 (Eq. 5)
Wherein
RLDUTInput return loss in dB for a DUT
ILDUTInsertion loss in dB for DUT
RLPIMOutput return loss in dB for PIM analyzer
The inequalities in equations 4 and 5 mean that S is greater than the input return loss of the DUT itself by at least 20dB if the sum of the round-trip insertion loss through the DUT and the output return loss of the PIM analyzer (in dB) is greater than the input return loss of the DUT itself11And S22The measurement error will be no worse than ± 1 dB.
For example, if the insertion loss of a reciprocal DUT is 10dB and the output return loss of the PIM analyzer is 15dB, then to measure S with an accuracy of + -1 dB11Or S22The input return loss of the DUT must be less than or equal to (2x10) + 15-20-15 dB.
Scalar S is performed using an enhanced response calibration method as described in Keysight Technologies and Potter but using a pair of in-line reflectometers instead of a conventional single port reflectometer and power meter21And S12The measurement is transmitted.
The enhanced response calibration method does not provide the same level of accuracy as the 10 or 12 error correction procedures due to the fact that it is not possible to correct the load mismatch presented by the PIM analyser on the DUT output port. However, this approach does correct for the source mismatch presented by the PIM analyser on the input port of the DUT.
To calibrate the system, OSL calibration is performed on each reflectometer. The reflectometers are then connected together at their test ports, and a receiver alignment procedure is performed in order to correct for the frequency errors that inevitably exist between the onboard RF source and the local oscillator in each instrument. This is followed by a normalization scan to determine the transmission tracking coefficients.
To perform scalar transmission measurements, a test signal is generated by a first reflectometer and applied to an input port of the DUT. The first reflectometer measures the reflection coefficient and incident power at the input port of the DUT, correcting for the effects of source mismatch. The power emerging from the output port of the DUT is measured using a back coupler in a second reflectometer. The scalar transmission coefficient is obtained by calculating the ratio of the received and transmitted power in watts and converting the result to decibels (dB). Alternatively, the same result can be obtained by taking the difference between the received power and the transmitted power in decibel-milliwatts (dBm).
In an alternative embodiment, the online vector reflectometer is modified to allow the stimulus level to be dynamically adjusted during the return loss scan in order to prevent saturation of the reflectometer's receiver. In such embodiments, a conventional PIM analyzer may be used, and dynamic source power control in an online vector reflectometer may be implemented in a variety of ways.
FIG. 11 shows a block diagram of a system 1100 for locating a fault in a DUT 605 in accordance with an embodiment of the invention. The system 1100 includes an online vector reflectometer 1105 similar to the reflectometer 615 of the system 600, but with a variable attenuator 1110 at the output of the RF source 230 (i.e., between the RF source 230 and the source coupler 235). Thus, a single port PIM analyzer 1115 may be used, which is a conventional PIM analyzer.
During the course of the return loss sweep, the reflectometer 1105 continuously monitors the receiver output level. In the event that either of these two signal levels falls outside acceptable limits, the control software of reflectometer 1105 suspends scanning and changes the setting of variable attenuator 1110 so that the signal level rises or falls to the appropriate level. The scan then restarts with the new settings and the process repeats until the end of the frequency sweep is reached.
Fig. 12 shows a method 1200 of return loss measurement according to an embodiment of the invention. The method 1200 may be implemented in the system 1100.
At step 1205, the reflection coefficient scan begins, much like in a conventional reflectometer, and at step 1210, the RF source is tuned to the next frequency point in the scan.
At step 1215, the amplitudes of the forward and reverse signals, and the phase offset between them, are measured, and if outside acceptable limits, the variable attenuator is adjusted in step 1225. Step 1215 is then repeated with the new settings.
If the amplitudes of the forward and reverse signals, and the phase offset between them, are within acceptable limits, then the vector reflection coefficients are calculated at step 1230.
At step 1235, it is determined whether the end of the scan has been reached. If not, the method repeats from step 1210 at the next frequency point in the scan. Optionally, a reflection coefficient scan is completed at 1240.
The system 1100 may be extended to a dual-port configuration that allows the forward and reverse PIM response of the DUT and the full dual-port S parameters to be measured in either direction.
Fig. 13 illustrates a system 1300 for locating a fault in a DUT 805 according to an embodiment of the invention. System 1300 is similar to system 900 of fig. 9, but has a dual port PIM analyzer 1305 without any limitation placed on its output return loss.
However, this creates a risk of a resonant mode being excited between the PIM analyser 1305 and the DUT 805 in case they have both a poor return loss at the S-parameter measurement frequency. This may occur between port 1820 a of PIM analyzer 1305 and DUT input port 825a, or between port 2820 b of PIM analyzer 1305 and DUT output port 825b, or on both ports. This in turn can cause receiver saturation in the S-parameter test set, resulting in a loss of measurement accuracy.
To prevent this from happening, a modified S-parameter test set 1310 is provided that includes a variable attenuator 1315 mounted to the output of the RF source 905 to allow for a reduction in stimulus level in the event that any received signal level exceeds the operating limits of the S-parameter test set. Variable attenuator 1315 is used in the same manner as attenuator 1110 of fig. 11, and method 1200 of fig. 12 may be utilized.
In particular, variable attenuator 1315 allows the test signal level to be dynamically adjusted to avoid receiver saturation in the S-parameter test set. Thus, there is no limit placed on the output return loss of the PIM analyzer, and thus the system 1300 may be used with PIM analyzers according to the prior art
In yet another embodiment, a fixed attenuator is inserted between the PIM analyzer and the online vector reflectometer to improve the output return loss of the PIM analyzer.
FIG. 14 shows a block diagram of a system 1400 for locating a fault in a DUT 605 in accordance with an embodiment of the invention. The system 1400 is similar to the system 1100, but includes a fixed attenuator 1405 between the PIM analyzer 1115 and the online vector reflectometer 1410, rather than having dynamic power control in the reflectometer 1410. The online reflectometer 1410 may be similar to or the same as the reflectometer 615 of fig. 6. There is no limit placed on the output return loss response of the PIM analyzer 1115 in the system 1400.
This configuration increases the output return loss of the PIM analyzer 1115 by an amount equal to twice the insertion loss of the attenuator 1405. With an appropriately selected attenuation level, it is possible to avoid saturating the reflectometer's receiver even if the highly reflective DUT 605 is measured at frequencies outside the transmit and receive frequency bands of the PIM analyzer 1115.
As an illustrative example, attenuator 1405 may have an insertion loss of 3 dB. This ensures that the worst-case output return loss of the PIM analyzer 1115 is at least 6dB (i.e., twice the insertion loss of the attenuator 1405), even in the stop-band of the PIM analyzer. In the case of a highly reflective DUT 605 (e.g., input return loss 0dB), then using equations 1 and 2, it can be seen that the maximum resonant induced power rise at the output of the forward and reverse couplers in the reflectometer is 6 dB. This is much lower than the 30dB power rise that would occur without the attenuator, thereby greatly reducing the risk of receiver saturation and the corresponding loss of measurement accuracy that accompanies it.
An attenuator mounted between the PIM analyser and the in-line reflectometer must generally be able to handle the peak instantaneous power in the two transmit carriers without experiencing dielectric breakdown, be able to dissipate the heat generated by the two transmit carriers as they pass through the attenuator without suffering damage or variations in the RF performance of the attenuator, and have a very low residual PIM (preferably less than-125 dBm @2x +43dBm per carrier power).
The system 1400 may be used with prior art in-line vector reflectometers. A conventional PIM analyzer may be used, provided that the PIM analyzer 1115 may increase its level of transmitted carriers sufficient to compensate for the insertion loss of the attenuator 1405. This is important because the PIM analyzer 1115 must still be able to test the DUT 605 in accordance with the IEC-62037 standard, which specifies that PIM testing on passive devices should be performed with a 2x +43dBm carrier applied at the input of the DUT 605. If the PIM analyzer 1115 cannot generate the desired transmit carrier level, it may be desirable to modify its design.
In this case, the PIM analyzer 1115 may be modified by: a) modifying the power amplifier to generate the necessary additional power; b) use of a power amplifier in a pulsed mode of operation rather than a Continuous Wave (CW) mode of operation, allowing higher power levels to be generated in short time intervals (e.g., 100 milliseconds); or c) combine the two transmit tones using a duplexer instead of a quadrature hybrid or a wilkinson combiner, thereby increasing the output power at the test port of the instrument by 3 dB.
The system 1400 is also extendable to a dual port configuration that allows measurement of both forward and reverse PIM responses and dual port S parameters of the DUT 805 in either direction.
FIG. 15 shows a block diagram of a system 1500 for locating a fault in a DUT 805 according to an embodiment of the invention. The system 1500 is similar to the system 800, but includes a fixed attenuator 1505 between the PIM analyzer 1305 and the online S parameter test set 1510. Online S parameter test set 1510 may be similar to or the same as test set 815 of fig. 8. Note that unlike system 800, there is no limitation placed on the output return loss response of PIM analyzer 1305 in system 1500.
In particular, a fader 1505 is installed on each port of the PIM analyser 1305, between the PIM analyser and the S-parameter test set 1510. Attenuator 1505 is a high power, low PIM attenuator to provide minimum guaranteed output return loss over a wide frequency range.
This arrangement is compatible with the 12-item and 10-item error correction procedures mentioned above, which are generally considered to be two of the most accurate S-parameter measurement techniques for two-port devices.
The performance requirements for attenuator 1505 are similar to those for attenuator 1405 and include high voltage breakdown strength, the ability to dissipate the necessary RF power without performance damage or change, and very low residual PIM.
The in-line full dual port S parameter test set 1510 may be implemented in a variety of ways, such as those mentioned above.
This is also the case for system 1400, where PIM analyser 1305 must be able to raise its transmit carrier level by a sufficient amount to compensate for the insertion loss of the attenuator. This ensures that the PIM analyzer can deliver 2x43dBm tones to the input ports of the DUT according to the IEC-62037 standard. If the PIM analyzer cannot increase its transmit carrier level by the required amount, the design of the PIM analyzer may need to be modified, as described with reference to PIM analyzer 1115.
FIG. 16 shows a block diagram of a system 1600 for locating a fault in a DUT 805 according to an embodiment of the invention. System 1600 is similar to system 1500, but includes a pair of online vector reflectometers 1605 between attenuator 1505 and DUT 805.
In particular, the dual port PIM analyzer 1305 is equipped with an attenuator 1505 on each of its test ports, and the output ports of the attenuator 1505 are connected to the upstream ports of a pair of in-line vector reflectometers 1605. The vector reflectometer 1605 may be similar to or the same as the vector reflectometer 1005 of FIG. 10. The test port of the vector reflectometer 1605 is connected to input and output ports of the DUT 805.
System 1600 can perform using the enhanced response calibration procedure mentioned aboveRow scalar S12And S21The procedure corrects for source mismatch but cannot correct for load mismatch, as measured. Thus, system 1600 does not provide the same level of accuracy as the 12-or 10-item error correction methods.
The system 1600 is also capable of executing a vector S11And S22The accuracy of the measurements, although, will vary depending on the insertion loss of the DUT 805, the output return loss of the PIM analyser 1305 and the return loss of the DUT 805 itself.
Equation 4 above can be used to ensure that at S11And S22Accuracy of ± 1dB of the measurement value.
The PIM or S-parameter tests described in the above embodiments may be performed at any suitable frequency band in the electromagnetic spectrum, including microwave, millimeter wave, and optical frequency bands.
The embodiments of the present invention described above enable an online vector reflectometer to perform vector reflection coefficient measurements over an unlimited frequency range when connected to a PIM analyser. The method and system may have particular utility in RTF modules, but is applicable to any online vector reflectometer.
An online vector reflectometer is provided that is extendable to a dual port online S-parameter measurement set that is capable of measuring all four S-parameters of a dual port DUT over an unlimited frequency range while connected to a dual port PIM analyzer.
In some embodiments, a broadband online single-port or dual-port S-parameter test set is provided that can be connected to a PIM analyzer so that the resulting device can measure PIM and S-parameters of a DUT without requiring any physical connection changes or RF switches.
The S-parameter test set enables accurate S-parameter measurements over a wide range of frequencies, including frequencies outside the transmit and receive bands of the PIM analyzer, even if the DUT is highly reflective. Furthermore, the S-parameter test set does not reduce the residual PIM response or noise floor of the PIM analyzer.
When a test set of S-parameters is connected between the PIM analyser and the DUT, the PIM analyser is able to apply 2 transmit carriers at a level of +43dBm per carrier to the input ports of the DUT according to the IEC-62037 standard ("passive RF and microwave devices, intermodulation level measurements").
Advantageously, VNA is no longer needed because broadband S-parameter measurements can be performed with an online vector reflectometer (or S-parameter test set) without compromising the operation of the PIM analyzer. This represents a large cost savings for the user, as VNAs are expensive to purchase and maintain.
Furthermore, the above-described systems and methods enable fast and efficient PIM and S parameter testing, as there is no need for any physical connection change from one test to the next. This further reduces wear on the DUT's connectors, as only one physical connection is needed in order to perform PIM and PIM tests.
Further again, embodiments of the present invention do not require an RF switch between the PIM and S-parameter test equipment, making it cheaper, faster and more reliable than RF switch-based solutions.
Finally, PIM and S parameter test results can be more easily collated into a final report due to the fact that they are obtained with a single integrated measurement system. This is faster, easier and less prone to error than trying to merge data from two separate test instruments.
In this specification and in the claims, if any, the word "comprising" and its derivatives, including "comprises" and "comprising", include each and every one of the stated integers but do not preclude the inclusion of one or more other integers.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.
In compliance with the statute, the invention has been described in language more or less specific as to structural or methodical features. It is to be understood that the invention is not limited to the specific features shown or described, since the means herein described comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.
Reference list
Rytting, "Network Analyzer Error Models and Calibration Methods" in 62 nd ARFTG Conference Short Course Notes of Boulder, 2003.
Keysight Technologies, "Applying Error Correction to Network analysis measures" Application Note 5965-.
Hiebel, Rohde & Schwarz, Fundamentals of Vector Network Analysis, 2007, pp 119-122.
Anritsu Company, "unwinding VNauthorization" Application Note111410-00673B, 12 months 2012.
Point, Boulder 1994, "improved Scalar Transmission measures Using Vector Source Match Correction" in the 44 th ARFTG Conference Digest of Boulder.
R.J.Cameron，“Design of manifold-coupled multiplexers”，IEEE MicrowaveMagazine 8，2007。

Claims (30)

1. A system for identifying faults in a radio frequency device under test, the system comprising:
a passive intermodulation test module configured to perform a passive intermodulation test of the device under test on at least one test port; and
an online S-parameter test set coupled to the passive intermodulation test module and interposed between the passive intermodulation test module and at least one test port and configured to perform a wideband S-parameter test of the device under test on the at least one test port.
2. The system of claim 1, wherein the passive intermodulation test module comprises:
a transmit module configured to provide at least one test signal on the at least one test port for passive intermodulation testing of the device under test; and
a receiving module configured to receive on the at least one test port a passive intermodulation signal generated by the device under test in response to the test signal.
3. A system for identifying faults in a radio frequency device under test, the system comprising a passive intermodulation test module configured to perform a passive intermodulation test of the device under test on at least one test port,
the passive intermodulation test module comprises:
a transmit module configured to provide at least one test signal on the at least one test port for passive intermodulation testing of the device under test; and
a receiving module configured to receive on the at least one test port a passive intermodulation signal generated by the device under test in response to the test signal.
4. The system of any one of claims 2 or 3, wherein the transmit module and the receive module are coupled to the at least one test port by a reflection-free multiplexer.
5. The system of claim 4, wherein the reflectionless multiplexer is a hybrid-coupled multiplexer.
6. The system of claim 5, wherein the mixer-coupled multiplexer comprises two or more independent channelized networks connected in cascade, followed by the matched load.
7. The system of claim 6, wherein at least one of the two or more independent channelization networks comprises two quadrature mixers and a pair of identical filters.
8. The system of any of claims 6 or 7, wherein each of the two or more independent channelization networks corresponds to a different frequency range.
9. The system of any of claims 6 to 8, wherein the two or more independent channelization networks include one channelization network that spans a transmit band of the passive intermodulation test module and a second channelization network that spans a receive band of the passive intermodulation test module.
10. The system of any of claims 1-9, wherein the passive intermodulation test module is capable of measuring passive intermodulation in two or more non-overlapping cellular frequency bands on a single test port.
11. The system of any of claims 1-10, wherein the passive intermodulation test module comprises a passive intermodulation analyzer having a single transmit band and a plurality of receive bands.
12. The system of any of claims 1 to 11, wherein the passive intermodulation test module is configured to perform passive intermodulation testing of the device under test on a plurality of test ports, an
Wherein the passive intermodulation test module is coupled to each of the plurality of test ports through one of a plurality of reflectionless multiplexers.
13. The system of claim 12, wherein each of the plurality of reflection-free multiplexers is coupled to the transmit module via a first RF switch, an
Wherein each of the reflectionless multiplexers is coupled to the receive module via a second RF switch.
14. The system of any one of claims 12 or 13, wherein at least one of the plurality of reflection-free multiplexers is a hybrid-coupled multiplexer.
15. The system of any of claims 3 to 14, further comprising:
an online S-parameter test set coupled to the passive intermodulation test module and interposed between the passive intermodulation test module and the at least one test port and configured to perform a wideband S-parameter test of the device under test on the at least one test port.
16. The system of any of claims 1,2, or 15, wherein the online S-parameter test set includes a fault range module.
17. The system of any of claims 1,2, 15, or 16, wherein the online S-parameter test set comprises a vector reflectometer.
18. The system of any of claims 1-2 or 15-17, wherein the at least one test port comprises a single test port.
19. The system of any of claims 1-2 or 15-18, wherein the at least one test port comprises two test ports.
20. The system of claim 19, wherein the online S-parameter test set comprises a two-port online S-parameter test set coupled to a first test port and a second test port of the two test ports.
21. The system of any of claims 1-2 or 15-20, wherein the online S-parameter test set includes separate first and second online reflectometers, wherein the first online reflectometer is coupled to the first test port and the second online reflectometer is coupled to the second test port.
22. The system of any of claims 1 to 2 or 15 to 21, wherein the online S-parameter test set comprises an RF source for generating test signals, the RF source being coupled through one or more directional couplers to an RF path between an input and an output of the online S-parameter test set.
23. The system of claim 22, wherein the S-parameter test set comprises a variable attenuator configured to provide dynamic source power control of the RF source.
24. The system of any of claims 1-2 or 15-23, comprising a fixed attenuator between the passive intermodulation test module and the online S-parameter test set.
25. A passive intermodulation test module configured to perform a passive intermodulation test of a device under test on at least one test port,
the passive intermodulation test module comprises:
a transmit module configured to provide at least one test signal on at least one test port for passive intermodulation testing of a device under test; and
a receiving module configured to receive on the at least one test port a passive intermodulation signal generated by the device under test in response to the test signal,
wherein the transmit module and the receive module are coupled to the at least one test port through a reflection-free multiplexer.
26. The passive intermodulation test module of claim 25, wherein the reflectionless multiplexer comprises a mixer-coupled multiplexer.
27. The passive intermodulation test module of claim 26 wherein the mixer-coupled multiplexer comprises two or more independent channelizing networks connected in cascade, followed by a matched load.
28. The passive intermodulation test module of claim 27 wherein at least one of the two or more independent channelization networks comprises two quadrature mixers and a pair of identical filters.
29. The passive intermodulation test module of any of claims 27 or 28 wherein each of the two or more independent channelization networks corresponds to a different frequency range.
30. The passive intermodulation test module of any of claims 27 to 29 wherein the two or more independent channelization networks comprise one channelization network spanning a transmit band of the passive intermodulation test module and a second channelization network spanning a receive band of the passive intermodulation test module.
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